Drvts improvements for soft timing
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drvTS improvements for soft timing. EPICS Collaboration Meeting Argonne National Laboratory June 2006 Matthias Clausen on behalf of Bernd Schoeneburg DESY Cryogenic Controls. Agenda. Time Requirements for Cryogenic Controls Soft Time Synchronization in EPICS Improved NTP Synchronization

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Drvts improvements for soft timing

drvTSimprovements for soft timing

EPICS Collaboration Meeting

Argonne National Laboratory

June 2006

Matthias Clausen on behalf of Bernd Schoeneburg

DESY Cryogenic Controls


Agenda

Agenda

  • Time Requirements for Cryogenic Controls

  • Soft Time Synchronization in EPICS

  • Improved NTP Synchronization

  • Network Delay Consideration

  • Compensating Clock Oscillator Errors

  • To Do / Nice to Have

Matthias Clausen, Bernd Schoeneburg, DESY

Cryogenic Control, 14-June-06


The requirements for cryogenic controls

The Requirements for Cryogenic Controls

  • 95% inputs are scanned periodically with 1 second.

  • Time accuracy in IOC should be < 1 second.

    • Soft (network) timing is sufficient

    • No event system

  • Many IOCs (~45) with different TS-configuration. Some can not be rebooted before a machine shutdown.

  • Accurate time is delivered by NTP servers outside the control network subnet.

Matthias Clausen, Bernd Schoeneburg, DESY

Cryogenic Control, 14-June-06


Existing 3 13 x epics implementation

Existing 3.13.x EPICS implementation

1: All IOCs are configured as timing slaves

  • IOCs have same and correct time if NTP-server is up.

  • no master allowed on subnet! All slaves would connect to master.

  • no time synchronization any more if NTP-server or gateway fails.

  • no time synchronization if the NTP-Server is not up at IOC boot time.

NTP

Server

network time protocol

Control Net

Gateway

DESY Net / WAN

IOC

Slave

IOC

Slave

IOC

Slave

IOC

Slave

IOC

Slave

Matthias Clausen, Bernd Schoeneburg, DESY

Cryogenic Control, 14-June-06


Existing 3 13 x epics implementation1

Existing 3.13.x EPICS implementation

2: Solution with a timing master

  • IOCs have the same time

  • IOC clocks are drifting with master clock (if no GPS-HW etc. is present)

  • Master can not synchronize with NTP-server.

not implemented

NTP

Server

EPICS time protocol

Control Net

Gateway

DESY Net / WAN

IOC

Slave

IOC

Slave

IOC

Slave

IOC

Slave

IOC

Master

Matthias Clausen, Bernd Schoeneburg, DESY

Cryogenic Control, 14-June-06


Improvements for soft timing

Improvements for Soft Timing

  • New mode (type) in TSconfigure

  • “type” is the last parameter in TSconfigure ().

  • 0 (default)= Use event system hardware, if present.

  • 1= Do not check if HW is present, use soft timing!

  • 2 (new)= Force to use NTP synchronization.

  • Mode 2 for timing slaves:

  • Like 1. Do not try to get time from Master, use NTP-Servers!

  • Mode 2 for timing masters:

  • Like 1. Start the synchronization task like a slave and use NTP to synchronize the internal time.

Matthias Clausen, Bernd Schoeneburg, DESY

Cryogenic Control, 14-June-06


Improvements for soft timing1

Improvements for Soft Timing

EPICS-TP and NTP is possible in parallel now

  • Slaves can select if they want the time from a master or NTP-server

  • Master can synchronize with NTP-server.

NTP

Server

EPICS time protocol

NTP

Control Net

Gateway

DESY Net / WAN

IOC

Slave

type 0

IOC

Slave

type 0

IOC

Slave

type 2

IOC

Slave

type 0

IOC

Master

type 2

Matthias Clausen, Bernd Schoeneburg, DESY

Cryogenic Control, 14-June-06


Improvements for soft timing2

Improvements for Soft Timing

  • Use more than one NTP-Server

  • The environment parameter “EPICS_TS_NTP_INET” can now contain a list of servers.

  • If the currently selected server fails, the next one will be used to get the time.

  • At boot time:

  • First try NTP to get the time from a server from the list.

  • Then try NTP to get it from the boot host.

  • At last try Unix time protocol to get it from the host.

  • Later synchronization:

  • Use NTP with servers from the list only.

Matthias Clausen, Bernd Schoeneburg, DESY

Cryogenic Control, 14-June-06


Improvements for soft timing3

Improvements for Soft Timing

  • Enhanced NTP Functionality

  • The network delay times are considered in a new function called “TSgetEpicsTimeFromNtpBuffer ()”.

NTP RX time

NTP TX time

NTP-server

NTP processing time

IOC TX time

IOC RX time

IOC

Net delay 2

Net delay 1

Time

T = NTPTX + ((IOCRX – IOCTX) – (NTPTX – NTPRX)) / 2

Matthias Clausen, Bernd Schoeneburg, DESY

Cryogenic Control, 14-June-06


Improvements for soft timing4

Improvements for Soft Timing

  • Internal Clock Correction

  • In spite of correct NTP or EPICS time synchronization, some IOC have wrong time of a few seconds – why?

    • When a ‘sync’ is done, the difference is scheduled to be driven to zero until the next expected synchronization.

    • But: During this time the clock of the IOC causes a new deviation if the frequency of the oscillator is wrong.

      • Need a correction of the frequency error!

      • existing offset correction is unchanged.

      • frequency correction runs continuously and is adjusted incrementally at each synchronization.

Matthias Clausen, Bernd Schoeneburg, DESY

Cryogenic Control, 14-June-06


Improvements for soft timing5

correction

Time

Sync 3

Sync 1

Sync 2

without frequency compensation

Diff

Time

freq-correction

Sync 3

Sync 1

Sync 2

with frequency compensation

Improvements for Soft Timing

Diff

Matthias Clausen, Bernd Schoeneburg, DESY

Cryogenic Control, 14-June-06


Results future plans

Results , Future Plans

  • Yes, it works.

  • The effect of network delay compensation is small. As long as the local time resolution is 1/60 second it works too coarsely for short delays! At the moment this functionality is disabled for delays <= 2 ticks.

  • It is implemented into R3.13.10 and can (should) be merged into R3.14.x.

  • The usage of a fast running timer (most BSPs support this) could be implemented.

    • Network delays could be compensated correctly.

    • Accurate timestamps were possible without extra hardware.

Matthias Clausen, Bernd Schoeneburg, DESY

Cryogenic Control, 14-June-06


Conclusion

Conclusion

  • Soft timing is now more comfortable

  • NTP and EPICS-TP can be used in parallel

  • More NTP servers can be used for redundancy

  • NTP network delays are compensated

  • Frequency error of the IOC clock oscillator is compensated

  • no 3.14 version yet

  • no fine resolution (accurate timestamp) yet

Matthias Clausen, Bernd Schoeneburg, DESY

Cryogenic Control, 14-June-06


Drvts improvements for soft timing

End

Thanks for your attention!

Matthias Clausen, Bernd Schoeneburg, DESY

Cryogenic Control, 14-June-06


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